Plasticity
The five water levels in the greenhouse significantly affected all
traits (Table 1, 2; Appendix Fig. S1), indicating plasticity in response
to water. Significant site × water interactions for all traits except
reproductive allocation (Table 2) indicated genetic variation in plastic
responses among the four sites of the rainfall gradient.
For the two sites with climate manipulations, the magnitude of
plasticity (quantified as CV) differed substantially among traits. CV
was lowest in δ 13C (3-4%) and days to
flowering (c. 10%), intermediate for diaspore weight, height, stomata
density, leaf number at flowering and total biomass, and particularly
high in reproductive allocation (c. 80%) and seed number (c. 100%)
(Fig. 3). The three traits showing rapid evolution thus had low (days to
flowering), intermediate (leaf number at flowering) and high plasticity
(reproductive allocation), respectively, signifying that plasticity and
the probability of rapid evolution in the field were independent.
Climate manipulations had overall little effect on the magnitude of
plasticity. Increased plasticity (CV) in plants from dry manipulated
plots compared to controls was found in diaspore weight (p=0.01) and a
similar non-significant tendency in days to flowering (p=0.06) (Table 3,
Fig. 3). Plasticity in vegetative biomass increased in dry plots
(p=0.03), but only compared to wet plots (Table 3, Fig. 3). The lack of
any significant climate manipulation × site interaction showed that
plasticity responded similarly to manipulations in both sites (Fig. 3,
Table 3). Moreover, plasticity (CV) was significantly higher in the
Mediterranean than the semi-arid site in four traits: days to flowering,
height, reproductive allocation, seed number (Table 3, Fig. 3). All
plasticity results were robust when using another common plasticity
index, PIv (Valladares et al. 2006).